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Kao K.-F.,National Tsing Hua University | Chang C.-C.,National Tsing Hua University | Chen F.T.,Industrial Technologies Research Institute | Tsai M.-J.,Industrial Technologies Research Institute | And 2 more authors.
Scripta Materialia | Year: 2010

We demonstrate two Sb-based alloys, Ga 25Te 8Sb 67 and Ga 18Te 12Sb 70, that have a crystallization temperature above 245 °C and activation energy of crystallization greater than 5 eV, for phase-change memory application. The temperature for 10 year data retention reaches 183 and 210 °C for Ga 18Te 12Sb 70 and Ga 25Te 8Sb 67, respectively. Test cells made of alloy Ga 25Te 8Sb 67 show similar memory switching behavior at pulse widths of 500-20 ns. Compared with the benchmark chalcogenide Ge 2Sb 2Te 5, the two antimonide alloys possess much improved thermal stability for applications in phase-change memory. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source


Kao K.-F.,National Tsing Hua University | Chu Y.-C.,National Tsing Hua University | Tsai M.-J.,Industrial Technologies Research Institute | Chin T.-S.,Feng Chia University
Journal of Applied Physics | Year: 2012

Thermal stability is one of the key issues in phase-change memory. We try to tackle it by developing new compositions based on Ga-Te-Sb system. Thermal stability is exemplified using Ga 18Te 12Sb 70 which shows crystallization-temperature (T x) 248 °C and activation energy of non-isothermal crystallization 5.9 eV. Films were isothermally soaked at 5 ∼ 30 °C below T x to estimate the failure-time when electrical resistance dropped to a half of the original. Arrhenius plot attained using logarithm failure-time versus reciprocal temperature were extrapolated to the temperature corresponding to 10-year failure (T 10y) as 183 °C. Pre-crystallization structure upon heating to 2 ∼ 5 °C below T x reflects stable amorphous phase of the alloy up to at least 240 °C. Memory-cells made of Ga 18Te 12Sb 70 can be set-reset at 20 ∼ 500 ns with electrical currents around 66 those of our Ge 2Sb 2Te 5 cells. We suggest that compositions Ga 18-25Te 8-12Sb 67-70 are optimal to ensure T x > 240 °C, T 10y > 180 °C and with low operation-currents. © 2012 American Institute of Physics. Source


Lee P.-H.,National Tsing Hua University | Chang P.-C.,National Tsing Hua University | Chao D.-S.,National Tsing Hua University | Liang J.-H.,National Tsing Hua University | And 3 more authors.
Thin Solid Films | Year: 2012

Crystallization and thermal stability of Ge 2Sb 2Te 5 (GST), the benchmark working material in phase-change non-volatile memory, were modified via Si-ion implantation. Through 5 × 10 15 Si-ions/cm 2 ion-implantation, crystallization temperature increases from 165°C to 177°C. Furthermore, the activation energy of crystallization increases from 2.9 eV in the pristine film to 3.3 eV and 4.0 eV in films implanted with the doses of 5 × 10 15 and 5 × 10 16 Si-ions/cm 2, respectively. Temperatures corresponding to a 10-year failure-time increase from 83°C in the pristine film to 96°C and 107°C in films implanted with 5 × 10 15 and 5 × 10 16 Si-ions/cm 2, respectively. Thermal stability of Si-ion implanted GST thus improves significantly. It was also found that grain growth is inhibited with higher implantation doses. In the case of the 5 × 10 16 ion/cm 2 dose, the second-phase transition from face-centered cubic to hexagonal closed-packed structure of the GST is completely inhibited. However, crystallization time increases slightly due to Si-ion implantation. © 2012 Elsevier B.V. All rights reserved. Source


Jimenez-Come M.J.,University of Cadiz | Munoz E.,Industrial Technologies Research Institute | Munoz E.,University of Cadiz | Garcia R.,Acerinox S.A. | And 3 more authors.
Advances in Intelligent and Soft Computing | Year: 2011

Different methods of classification have been used in this paper to model pitting corrosion behaviour of austenitic stainless steel EN 1.4404. This material was subjected to electrochemical polarization tests in aqueous environment of varying chloride ion concentration (from NaCl solutions), pH values and temperature in order to determine values of critical pitting potentials (Epit) for each condition tested. In this way, the classification methods employed try to simulate the relation between E pit and those various environmental parameters studied. Different techniques have been used: Classification Trees (CT), Discriminant Analysis (DA), K-Nearest-Neighbours (K-NN), Backpropagation Neural Networks (BPNN) and Support Vector Machine (SVM). These models have generally been regarded as successful. They have been able to give a good correlation between experimental and predicted data. The analysis of the results becomes useful to plan improvement in the austenitic stainless steel protection and to avoid critical conditions expositures of this material. © 2011 Springer-Verlag Berlin Heidelberg. Source


Wang S.-H.,National Tsing Hua University | Chin T.-S.,National Tsing Hua University | Chin T.-S.,Feng Chia University | Yang C.-F.,National Tsing Hua University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2010

We investigated the effect of Ge additions (0.1-0.5 at.%) on properties of Sn84Zn13Bi3 solder-alloys, specifically the anti-oxidation capability, electrical resistance, thermal expansion behavior, and mechanical strength. The Sn-Zn-Bi-Ge alloys have a melting point around 197 °C, and are not noticeably oxidized after soaking at 250 °C for 180 min under ambient air flow 100 ml/min. Coefficient of thermal expansion, tunable between 10 and 17 ppm/°C by the Ge addition, matches those of various metals such as Cu, Ni or lead-frames, leading to low thermal stress. Electrical resistivity of Sn-Zn-Bi-Ge solder-alloys, 10-15 μΩ cm, is much lower than that of Sn-37Pb solder. The micro-Vickers hardness, up to 400 MPa with 0.5 at.% Ge addition, is 150% that of Ge-free Sn84Zn13Bi3, or 300% that of Sn-37Pb solder. Moreover, it possesses better tensile strength, being 127% that of Ge-free Sn84Zn13Bi3, and 190% that of Sn-37Pb solder. © 2010 Elsevier B.V. All rights reserved. Source

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